If you’re using a smartphone, it will keep a record of the mobile carrier, while internet service providers (ISPs) will be stored for users using a Wi-Fi or Ethernet connection to access Facebook.

In some cases, it will monitor devices that are using the same network as you.

‘Facebook’s services inherently operate on a cross-device basis: understanding when people use our services across multiple devices helps us provide the same personalized experience wherever people use Facebook,’ the firm wrote in the lengthy document.

According to Facebook, this is done, for example, ‘to ensure that a person’s News Feed or profile contains the same content whether they access our services on their mobile phone or in a desktop computer’s web browser.’

Facebook also says this information is used to curate more personalized ads.